JP2002139010A - Screw with thin head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw with a relatively thin head and a small nominal diameter, having sufficient strength for assembling parts. SOLUTION: The screw with the thin head, consisting of the head 2 and a leg 4, has a large-radius circular face formed on a top face 5 of the head, a tapered non-screw portion 20 formed between a bearing surface 6 and a ridge 3 and an arcuate portion 21 continuously provided on the ridge side. The screw can be manufactured in application for small products and satisfactorily used in application for thin products. Since the non-screw portion and the ridge are connected via the arcuate portion, no stress concentration and fatigue failure occur during screwing or with the passage of a long time after screwing, therefore producing sufficient fastening force. If heat treatment and gilding treatment are applied to a screw material, the heads are prevented to adhere with each other during a great amount of work because the top faces of the heads are not flat, resulting in stable heat treatment and gilding treatment to be kept at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for screwing a work into a work without impairing the aesthetics of the work even if the head of the screw protrudes from the work. Screw with thin head that can be used without any problems.

[0002]

2. Description of the Related Art In recent electrical appliances and information equipment products, those having improved performance and relatively small size are often used. Among them, thin products such as thin ones for easy carrying are used. Electronic devices such as electronic notebooks, notebook computers, and mobile phones are rapidly and widely used. Such a product must be as light as possible and have a small thickness so that it can be easily carried.
At present, small screws of not more than mm are used. For this reason, in recent years, a screw having a size as small as possible has been developed. However, as shown in FIG.
Because the head 102 of No. 01 forms a cross-shaped engaging groove 105 that engages with the driver bit, the shape of the head 102 is still a standard with respect to the nominal size of the screw set by JIS (Japanese Industrial Standard). Head height.
Under such circumstances, recently, a head whose head is relatively thinner than the standard screw head thickness has been demanded, and a screw 201 as shown in FIG. The fastening member 232 is being fixed to the work 230.

[0003] In addition, there is a screw having a similar shape as shown in FIG. This is a utility model which was published as Japanese Utility Model Publication No. 38-10834 in 1963, and has a round plate head 302 integrally formed at the upper end of a main rod 304, and a maximum diameter of the round plate head 302. A flat flange 305 is integrally provided on the outer circumference, a cross hole 310 for driver fitting is formed in the head 302 of the round plate head, and a conical portion (not shown) is formed below the main rod 304. , And a screw thread 303 having the same pitch which is continuous with the main rod 304 and the conical portion is formed integrally. This screw was not originally designed to assemble a relatively thin product, but was intended to provide a screw in which the screw head and washer were integrated. Overall, it was still large, and this screw was far from the consumer's demand for assembling thinner products.

[0004]

However, despite the demand for such a thin product,
Since there is a limit to the miniaturization of the screw, the inability to cope with miniaturization of the product has a sense of danger that future assembly operations will be greatly affected. In order to eliminate this sense of crisis, screws with a thinner head than those of conventional screws with only a small nominal diameter have been developed and are being used. Since there is an engagement groove in the head where the driver bit engages, the portion at this portion becomes brittle because the thickness of the portion becomes thin. In particular, since the engaging groove reaches the leg of the screw, the material near the engaging groove of the leg is thinned or torn, and a sufficient function as a screw is not obtained. In addition, when the screw material is subjected to heat treatment and plating to give necessary strength to the screw, if the top surface of the head is flat, the volume of the head is small,
During a large amount of processing work, the heads are in close contact with each other,
Heat treatment and plating are incomplete.

In order to solve this problem, the one shown in FIG. 7 is being used. However, since the thickness of the head is made thinner than the standard one, the engagement groove is formed in this screw. Between the head and the screw thread, there is formed a screwless portion constituting a tapered reinforcing portion having a relatively large diameter on the head side. In this manner, the occurrence of a thin portion caused by forming the engagement groove is eliminated. By eliminating the occurrence of thin portions with such a configuration, even if a predetermined screwing force is applied to this screw, it is prevented that the screw is broken, but on the other hand, the gap between the screw thread and the head Has a threadless portion, and since a thread is formed subsequently, a corner is formed between the threadless portion and the thread. Stress concentration occurs, the screw is broken at the time of screwing, and fatigue is accumulated in the screw with the passage of time, and fatigue fracture of the screw is likely to occur. Also,
During the molding of the head, the movement of the screw material that occurs during the molding of the cross hole has a small taper angle of the threadless portion with respect to the outer wall angle of the cross hole, so that the flow of the material is poor, so it is used for molding work. There is a problem that the life of the punch and the receiving piece is shortened.

SUMMARY OF THE INVENTION An object of the present invention is to provide a screw which solves such a problem and which has a relatively small head thickness and a sufficient strength to assemble parts even with a screw having a small nominal diameter. is there.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a head 2 having an engaging groove 10 in which a driver bit for transmitting a driving force is engaged, and a head 3 integral with the head 2 and having a thread 3. In the screw 1 composed of the legs 4 formed with a circle, an arc surface having a relatively large radius is formed on the top surface 5 of the head, and the screw surface 3 of the head 4 and the thread 3 of the legs 4 are formed. Tapered threadless portion 2 formed with a large head side and a small thread side of leg 4
And an arc-shaped portion 2 having a curved cross-section so as to be continuously connected to the thread side of the threadless portion 20.
This is achieved by providing a screw having a thin head provided with a one. In order to achieve this object, the angle α forming the outer peripheral surface of the screwless portion 20 having the above configuration is larger than the angle β of the outer wall 11 forming the engagement groove 10 formed in the head 2 of the screw 1. It may be a screw having an enlarged and thin head. Further, in addition to these configurations, the leg 4 on which the screw thread 3 is formed has a substantially triangular cross-sectional shape, and the prepared female screw 31 of the prepared hole formed in the work 30 is formed by three substantially triangular vertices. It may be a screw having a thin head that is configured. In addition to the above purpose, the head 2 has a curved portion 7 having a curved cross-sectional shape from the center of the head 2 to the outer peripheral edge on the seating surface 6 thereof, and the head 2 has a nominal diameter d of the screw 1 of 2.5. It is also achieved by providing a screw having a thinner head formed with an outer diameter dimension of about three times as large.

[0008]

FIG. 1 is a block diagram showing an embodiment of the present invention.
6 through FIG. 1 and 2, 1
Is a screw composed of a head 2 and a leg 4 integral with the head 2 and having a thread 3. The head 2 of the screw 1 is formed with a cruciform conical engagement groove 10 which can be engaged with a driver bit (not shown) for transmitting a driving force on the center line of the leg 4. The tip of the groove 10 reaches the leg 4. The outer wall 11 of the engagement groove 10 is inclined toward the center of the leg 4 as it becomes deeper from the top surface 5 of the head 2 to the leg 4. The head 2 is formed to be relatively thinner than the head 2 of the ordinary screw 1.
The maximum thickness of the head 2 before the 0 is formed is set to about 1/3 or less of the nominal diameter of the screw 1. The top surface 5 of the head 2 is a spherical arc surface with a relatively large radius, and the outer peripheral edge of the head 2 is thinner than the thickness at the center. The outer diameter of the head 2 is formed to be about 2.5 to 3 times the nominal diameter of the screw 1. In particular, the size of 3 times the nominal diameter is equal to the head 2 diameter.
Due to the fluidity of the screw material in the forging process, there is a limit to the outer diameter of the head where defective products such as underfill or cracking occur depending on the material. For this reason, the maximum value is set to three times or less.

As shown in FIG. 1, the head 4 is located between the seat 4 and the thread 3 of the leg 4 at a position close to the seat 6 of the head 2. A screwless portion 20 having a tapered shape with a large portion side and a small leg portion is formed, and the position of the screwless portion 20 connected to the seat surface 6 on the head side is the leg portion 4.
Is located outside the center of the screw 1 from the outer diameter position of the thread 3 formed at the center. The threadless portion 20 has a predetermined thickness between the outer wall 11 of the engagement groove 10 and the threadless portion 20 is formed to have a sufficient diameter larger than the thread outer diameter to form this thickness. ing. The angle α forming the outer peripheral surface of the screwless portion 20 is larger than the angle β of the outer wall 11 forming the engaging groove 10 formed in the head 2 of the screw 1. This makes the molding flow of the material smooth during the forging. on the other hand,
An arc-shaped portion 21 having a curved cross section is formed on the thread side of the threadless portion 20 so as to be continuously connected thereto, and the thread 3 is formed continuously from the arc-shaped portion 21. Therefore, stress concentration in this portion during fastening with the screw 1 is less likely to occur.

Further, the thread 3 is formed at the lower portion of the threadless portion 20 so as to extend to the tip of the leg 4, and the thread 3 has a substantially triangular leg cross section as shown in FIG. Formed on the leg portion 4. In this embodiment, the leg 4 has a substantially triangular shape. Alternatively, the leg 4 may have a circular shape. By forming the leg 4 into a substantially triangular shape, the female screw 31 is formed in a prepared hole (not shown) of the work 30. In the operation of screwing in while performing the operation, a smooth screwing operation can be obtained.

In the operation of screwing into the work 30 by using such a thin-headed screw 1, as shown in FIG.
A driver bit is engaged with the engagement groove 10 of the screw 1 with respect to the prepared hole of the work 30 to transmit the screwing force and screw the screw. At this time, the screwing force from the driver bit is transmitted from the screwless portion 20 to the leg 4 and the thread 3 is
With a predetermined screwing force. On the other hand, the work 30
The member to be fastened 32 has a mounting hole 33 sufficient to receive the threadless portion 20 in advance, and the seating surface 6 of the head 2 is seated on the surface of the member to be fastened 32. I have.

When the screw 1 is screwed in after the member to be fastened 32 is made to coincide with the prepared hole of the work 30, as shown in FIG. The screw 3 is screwed while forming the female screw 31 at the thread 3, that is, the three vertices of a substantially triangular shape. When the screw 1 is screwed in this way and the seat surface 6 of the head 2 is seated on the member 32 to be fastened, the screwing operation is completed.

The screw 1 shown in FIG.
In the above, a so-called head seat surface 6 having a spring effect is formed by forming a curved portion 7 having a curved cross-sectional shape from the center of the head 2 to the outer peripheral edge on the seat surface 6 of the head 2. After the screw 1 is screwed in, the head seat surface 6 is seated on the member 32 to be fastened, as shown in FIG.
Of the screw 1, a spring effect is generated, and a loosening force generated between the screw 1 and the work 30 is prevented.

[0014]

As is apparent from the embodiments described above, the present invention comprises a head 2 having an engaging groove 10 and a leg 4 integrally formed with the head 2 and having a thread 3 formed thereon. In the screw 1, an arc surface having a relatively large radius is formed on the top surface 5 of the head, and the head side is large and the screw side is small between the seating surface 6 of the head 2 and the thread 3 of the leg 4. A tapered screwless portion 20 is formed, and an arc-shaped portion 2 having a curved cross section is formed continuously on the thread side of the screwless portion 20.
Since the screw has a thin head provided with 1, it is possible to reliably manufacture a screw for a miniaturized product as at present, and to use the screw for a small and thin product in the future. We can cope enough. Further, since the threadless portion 20 and the screw thread 3 are connected by the arcuate portion 21 having an arc shape, stress concentration does not occur at the time of screwing into the portion or even after a long time after being screwed into the portion. Since no breakage occurs, a sufficient fastening force can be obtained as a screw. Furthermore, when the screw material is subjected to heat treatment and plating to give the necessary strength to the screw, the head surfaces are not flat, so that the heads do not adhere to each other during a large amount of processing work. , Heat treatment and plating are always stable.

The threadless portion 20 has an engagement groove 1 formed at the head 2 of the screw 1 with an angle α forming an outer peripheral surface thereof.
0, the thickness of the head is smaller than the angle β of the outer wall 11, so that the material flow of the screw material at the time of forging the screw becomes smooth, and the life of the punch and the receiving piece used in the forming operation is also increased. It is long, and the head forming defect is reduced, and the strength of the screw neck is also improved. Furthermore,
The leg 4 on which the thread 3 is formed has a substantially triangular cross-sectional shape.
Since the female screw 31 of the lower hole of the work 30 is formed by three vertices of a substantially triangular shape, the work of screwing while forming the female screw in the lower hole of the work may be performed with a relatively low screwing torque, and the smooth screwing operation is performed. Will be possible. Moreover,
Since the head 2 is formed with a curved portion 7 having a curved cross-sectional shape from the center of the head 2 to the outer peripheral edge on the seating surface 6 thereof, even when a vibration is generated due to the spring effect exerted on the head during screwing. Screws are not easily loosened. In addition, the formation of the curved portion increases the fastening force at the time of screwing, so that a stronger holding force can be obtained. On the other hand, since the head has a small thickness formed with an outer diameter dimension of about 2.5 to 3 times the nominal diameter d of the screw, it is reliable even if the area seated on the member to be fastened is large. There are specific effects such as obtaining a holding force.

[Brief description of the drawings]

FIG. 1 is a sectional front view of a main part of a thin-headed screw according to an embodiment of the present invention.

FIG. 2 is a bottom view of FIG.

FIG. 3 is a sectional front view of a main part showing a use state of the present invention.

FIG. 4 is an enlarged sectional view of a main part of FIG.

FIG. 5 is a cross-sectional front view of a main part showing another embodiment of the present invention.

FIG. 6 is a cross-sectional view of a main part showing a use state of a screw according to another embodiment of the present invention.

FIG. 7 is a sectional view showing a conventional example of the present invention.

FIG. 8 is a sectional view showing another conventional example of the present invention.

FIG. 9 is a cross-sectional front view of a main part showing still another conventional example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw 2 Head 3 Thread 4 Leg 5 Top surface 6 Seat surface 7 Curved portion 10 Engagement groove 11 Outer side wall 20 Threadless portion 21 Arc-shaped portion 30 Work 31 Female screw 32 Fastened member 33 Mounting hole

Claims (5)

[Claims] 1. A head (2) having an engaging groove (10) for engaging a driver bit for transmitting a driving force, and a leg integrally formed with the head and having a thread (3). Department (4)
Forming a circular arc surface with a relatively large radius on the top surface (5) of the head,
A tapered screwless portion (20) is formed between the seat surface (6) of the head and the thread of the leg, the head side being large and the thread side of the leg being small. A screw having a thin head, characterized in that an arc-shaped portion (21) having a curved cross section is provided on the thread side so as to be continuously connected thereto. 2. An angle .alpha. Forming an outer peripheral surface of the screwless portion is larger than an angle .beta. Of an outer wall (11) forming an engaging groove formed in a head of the screw. A screw having a thin head according to claim 1. 3. The thread-formed leg portion has a substantially triangular cross-sectional shape, and a female screw (31) of a prepared hole formed in the work (30) is formed by three apexes of a substantially triangular shape. A screw having a thin head as claimed in claim 1 or claim 2. 4. The thickness of the head according to claim 1, wherein the head has a curved portion having a curved cross-sectional shape from the center of the head to the outer peripheral edge of the seat. Screw with a thin head. 5. The thickness according to claim 1, wherein the head has an outer diameter of about 2.5 to 3 times the nominal diameter d of the screw. Screw with thin head.